1. Field of the Invention
The present invention relates to a recording head for an ink-jet printer.
2. Description of the Related Art
A former recording head for an ink-jet printer has a common ink chamber communicated with an ink cartridge and has a plurality of ink-jet nozzles connected in parallel to the common ink chamber. The interior of each of the ink-jet nozzles is communicated with the common ink chamber. A hole is formed in a base portion of each of the ink-jet nozzles to secure a flow rate of ink discharged to the exterior of each of the ink-jet nozzles. The hole has a diameter larger than a diameter of an ink discharging orifice disposed at an end tip of each of the ink-jet nozzles.
In the above former recording head, when the supply of ink from the ink cartridge to the common ink chamber is interrupted and a printing operation is further performed continuously, air is flowed into an interior of a certain ink-jet nozzle among the plural ink-jet nozzles through the ink discharging orifice of this ink-jet nozzle. At this time, the other ink-jet nozzles except for this ink-jet nozzle having the intake air robs this ink-jet nozzle of its ink and continuously discharges this ink. Accordingly, air is further flowed into this ink-jet nozzle having the intake air. As a result, the ink-jet nozzle having the intake air has an amount of the air sufficient to make the air reach into a deep portion of this ink-jet nozzle.
No former recording head has a means for preventing the air from being further flowed into the deep portion in an intermediate portion of an intake path of the air within the recording head. Therefore, the air is flowed into the common ink chamber so that the ink-jet nozzle falls into a condition to be difficult or impossible to return its function to the original state.
The former recording head for an ink-jet printer will next be described with reference to FIGS. 4a to 6 to clarify the principle of a recording head in the present invention.
FIG. 4a is an explanatory view for showing the relation in position between a recording head 2 and an ink cartridge 3 in an ink-jet printer 1. FIG. 4b is a transverse cross-sectional view of the ink-jet printer shown in FIG. 4a.
As shown in FIGS. 4aand 4b, the ink-jet printer 1 is constructed by the recording head 2 and the ink cartridge 3. The ink cartridge 3 is connected to the recording head 2 through a flowing passage of ink. The recording head 2 has a common ink chamber 4 and a plurality of ink-jet nozzles 5 connected in parallel to the common ink chamber 4. In the former printer, a hole 7 is disposed in a connection portion between the common ink chamber 4 and each of the ink-jet nozzles 5 to secure a flow rate of ink such that a diameter of this hole 7 is larger than that of an ink discharging orifice 6.
An oscillator disposed in each of the ink-jet nozzles 5 is omitted in FIG. 4b.
FIG. 5 is a cross-sectional view taken along line A--A of FIG. 4b. An ink supply port 8 is disposed in the common ink chamber 4 and is communicated with the ink cartridge 3. The hole 7 is formed in a base portion of each of the ink-jet nozzles 5 to flow ink taken into the common ink chamber 4 through the ink supply port 8 to each of the ink-jet nozzles 5. An oscillator 9 is arranged within each of the ink-jet nozzles 5 to discharge the ink flowed into each of the ink-jet nozzles 5 through the hole 7 to the exterior of each of the ink-jet nozzles 5 through the ink discharging orifice 6.
FIGS. 6a, 6b and 6c are views for schematically showing the flowing processes of the air flowed into the recording head for an ink-jet printer when the supply of ink from an ink cartridge is interrupted in the former recording head. No oscillator is illustrated in FIGS. 6a 6b and 6c.
As shown in FIG. 6a, when the supply of ink from the ink cartridge is interrupted and a printing operation is further performed continuously, the air is flowed into a certain ink-jet nozzle 5 through an ink discharging orifice 6 thereof. This certain ink-jet nozzle 5 is set to the second ink-jet nozzle from the left-hand side in FIG. 6a. (Reference numeral 30 designates ink.) The other ink-jet nozzles except for this ink-jet nozzle 5 having the intake air robs this ink-jet nozzle of its ink and continuously discharges this ink. Therefore, as shown in FIG. 6b, the air is flowed into a deeper portion of this second ink-jet nozzle 5. In the former ink-jet nozzle, a diameter of the hole 7 is set to be larger than that of the ink discharging orifice 6. Accordingly, it is impossible to prevent the intake air from being further flowed into this ink-jet nozzle 5. Therefore, as shown in FIG. 6c, the intake air within this ink-jet nozzle 5 is further flowed into the common ink chamber 4 so that this ink-jet nozzle 5 falls into a condition to be difficult or impossible to return its function to the original state.
To avoid such a state, it is necessary to detect a remaining amount of ink within the ink cartridge and stop the printing operation when this remaining amount is small.